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SALICYLALDEHYDE                           189

through the top of the condenser and, after each addition, the
flask is well shaken. A gentle reaction sets in, and the temper-
ature rises. At the same lime the surface of the brownish
yellow solution takes a violet tint, which rapidly fades, the
liquid finally assuming1 a deep red colour. When all the chloro-
form has been added, the contents of the flask are boiled for half
an hour. A yellow semi-solid mass separates out of the solution.
The imattackcd chloroform is now distilled off on the water-
bath, the liquid diluted with water and strongly acidified with
dilute hydrochloric or sulphuric acid. A thick red oil separates
out on the surface and is subjected to distillation in steam. An
oil, having a faintly yellow colour, distils over with the water, and-
settles to the botlprn'o'f the receiver. When drops of oil cease
to condense, the distillation is stopped. The distillate, which con-
tains salicylaldchyde and phenol, is extracted with ether, and the
ethereal solution well shaken with a saturated solution of sodium
bisulphite (see Reaction 2, *p. 67). The bisulphite compound
of salicylaldchyde separates out in colourless needles, which are
filtered, washed free from traces of phenol with alcohol and then
decomposed by heating with dilute sulphuric acid. The aldehyde
which separates is taken up with ether, dehydrated over calcium
chloride, the ether driven off and the aldehyde distilled.
Yield, 10 grams. In the distilling flask from which the saliryl-
aldehyde has in the first instance been removed with steam,
there remains a brownish liquid and a dark red substance, which
sinks to the bottom of the vessel, and forms a brittle resin on
cooling. The aqueous portion is filtered hot through a moistened
filter, which retains the resin, and the filtrate, containing /;-hydr-
oxybenzaldehydc, is extracted when cold with ether. On distilling
off the solvent, the aldehyde remains in the form of a yellow
mass of stellar-shaped needles, which may be purified by
crystallisation from hot water. Yield, about 2 grams.

CMClfl - Co

. Colourless fragrant oil, b. p.
196*5^; i '173 at 13*5; solidifies at 20", forming large
crystals. . Volatile in sttia-m ; soluble in water ; miscible in all
proportions with alcohol and ether.